At a high level, the reason is pretty simple. Because it isn’t core to their business and doesn’t make financial sense. Let’s break it down.
Amazon and Microsoft earn significant portions of their revenue from commercial and enterprise services, which involves cloud infrastructure; providing both IaaS (Infrastructure-as-a-Service) and PaaS (Platform-as-a-Service). And in the case of Microsoft, SaaS (Software-as-a-Service) in the form of Office 365 and Dynamics. As such, these two companies have built the two largest cloud platforms in the world. In fact, their cloud infrastructures are so far ahead (size and capability) of their closest rivals (IBM and Google) that the industry coined a new term to describe them; hyperscale clouds. But the important takeaway here is that enterpirse services are core to their businesses, so investments in data center development and operations, as well as service development and management, is critical to them. And they have built significant technical and operations capabilities to manage them.
Google, on the other hand, has a business model that benefits greatly from operating their own cloud. But their infrastructure investments have been focused more on ensuring quality-of-service (QoS) and control of their IT/OT than being an IaaS or PaaS provider. To compete with Amazon and Microsoft in this area, Google would need to significantly expand its global footprint, build many more services and capabilities, and add proficiency in industry and enterprise account management and QoS. None of which help improve the profitability of their core business, search. That said, Google probably wants to diversify and has said that they wish to compete more aggressively and efficiently in cloud. So this looks like a challenge they intend to tackle. And this makes sense given they view Amazon as a significant competitor cross their lines of business.
This bring us to your question about Facebook, which operates a few of their own data centers and founded the Open Compute Project to collaborate on open, scalable computing. But their mission is similar to Google. Facebook is focused on QoS and managing their own operations including compute for Facebook’s data graph. Facebook has virtually no service infrastructure to provide IaaS or PaaS capabilities, and lacks any credibility or capability in business-to-business services and account management. To try and compete in this space would be a huge departure from their core business and cost them so much money that their primary business and customer base would suffer.
When businesses chose to enter new markets, they do so carefully. They want these investments to add value in their current businesses and position them to capture new revenue streams. But they also need to be sure that they can differentiate and compete effectively. And for Facebook, becoming a cloud platform provider is a distraction that makes no sense.
